Self-loading ambulance stretchers have a platform on which the patient is laid, and a frame for supporting said platform, which in turn has legs with free wheels for transfer thereof.
As the stretcher is loaded onto the ambulance, the operator has to push it along the ambulance floor, wherefore the legs have to be somehow folded against the frame; this can be accomplished manually (according to a rather obsolete practice), or using special arrangements, such as hinging the legs under the floor for later unlocking thereof towards the floor by suitable hydraulic or mechanical or electric devices as the stretcher is pushed by the operator.
In another type of stretcher the wheels are mounted to a lower frame, which is connected to the upper frame, the platform being fixed thereto by one or more scissor-lift systems: thus, the loading step is carried out by laying the front of the stretcher, usually equipped with additional wheels, on the ambulance floor and by causing the stretcher to collapse by folding the above mentioned scissor-lift, i.e. by lifting the lower frame against the upper frame until the free wheels of the lower frame are flush with the ambulance frame, whereby the operator can push the collapsed stretcher into the ambulance.
Concerning this action, a major drawback arises in that at least two operators are needed, with the former holding one end of the stretcher (the other end already lying by suitable front loading wheels on the ambulance floor), and the latter moving the lower frame towards the main frame, thereby folding the scissor-lift system. The same drawback arises when the stretcher has to be unloaded from the ambulance.
Furthermore, while one operator operates the scissor-lift, the other has to support the combined weight of the stretcher and the patient lying thereon, and with time this may cause the operator to suffer pain o injury.